Hydraulic pumping system



June 25, 1963 R. B. JOHNSTON 3,094,842

HYDRAULIC PUMPING SYSTEM Filed April 21, 1961 5 Sheets-Sheet 1 m 7- vr/i' I I W34 22 I J0 fl 24a 3/ /2 N L/ L 1 -/4 1% Q 1 38 /J 25 e I 2/ ll37 /6 250' I o {I 36 P L P /7 i 63 20 Z6 Z9 28 /l K '7 2.4% J2 A? 342.90 /9 o QR I z 2567\ V I 35 E /7 33 P P a 35 /74 23 INV EN TOR.

/5 23a M m ATTORNEYS June 25, 1963 R. B. JOHNSTON 3,094,842

HYDRAULIC PUMPING SYSTEM Filed April 21, 1961 3 Sheets-Sheet 2 :4 22 i lf /3 22A I J 14 15/ 39 A 35 a v 1 P f J 6 0/921 da/znJzari /5 INVENTOR.

ATTORNEY? June 25, 1963 3,094,842

R. B. JOHNSTON HYDRAULIQPUMPING SYSTEM fiufz/J 49. (/0/7/74" fafl IN VENTOR.

States Unite This invention relates to reciprocable hydraulic pumpingsystems of the balanced type. More particularly, it relates toimprovements in systems of this type wherein the pistons of a pair ofmotor cylinders are reciprocated by a single power unit and the weightof the rod for one piston is counterbalanced by the weight of the rodfor the other piston.

Systems of this type are particularly well suited to the pumping of deepwells or other applications where the rod weight comprises a majorfactor in the power required to reciprocate the pistons. With the rodweight counterbalanced, the power unit need only lift the weight of thewell fluid being pumped, as well as extra loads due to friction andother relatively minor factors which may be ignored; In such systems,the lower sides of the pistons are fluidly connected by a balance line,and the power unit is alternately connected to the upper side of firstone and then the other piston so as to reciprocate them in oppositedirections within the cylinders. If desired, each rod may be connectedto thedown-the-hole pump of a well so that both wells are pumped by thesingle power unit. On the other hand, the system contemplates that onepiston may be counterbalanced by some means other than well fluid.

Previous systems of this type have employed unduly complicatedmechanisms for operating a reversing valve in shifting the power fluidfrom the upper side of one piston to the upper side of the other.Apparently, the presence of power fluid above the pistons has precludedothers from attempting to accomplish this shifting of the reversingvalve with the ordinary check valve-controlled lines.

Some in this field have used a closed system wherein the power fluidfrom above one piston discharges into the pump suction. This requiresthe use of high rate-d pumps, and may even put conventional pumps out ofthe usable range. Others have suggested a single system for supplyingpower to the motor pistons as well as for replacing hydraulic fluid lostfrom the system during its operation. In such an arrangement, the singlepump must raise the pressure of the power fluid to above that in thebalance line, which is impractical in view of the volume of power fluidrequired. Also, such systems ordinarily have complex arrangements fordumping an excess of such replenished fluid to maintain the motorpistons properly synchronized.

An object of this invention is to provide a system of the type describedin which the shifting of the reversing valve is accomplished with themore conventional and simplified shifting lines.

Another object is to provide a system of this type having a pump with anon-pressurized or atmospheric suction as well as a separate pump forreplenishing lost fluid.

A further object is to provide such a system having a simplifiedarrangement for dumping excess fluid, and, more particularly, one whichrequires no additional valves.

Still another object is to provide such a system which is easy to start,and especially one which does not require preparation, such as theopening and closing of valves, prior to starting.

Yet another object is to provide a simplified reversing valve andattendant parts for such a system, and more atent O 3,094,842 PatentedJune 25, 1963 particularly a spool valve for this purpose havingconventional outwardly urged sealing rings thereabout.

-In the drawings, wherein like reference characters are used throughoutto designate like parts:

FIG. 1 is a diagrammatic illustration of a system constructed inaccordance with one embodiment of the invention, and at a stage of itsoperation wherein the piston in the leftmost or control cylinder isbeing raised and the piston in the rightmost or slave cylinder lowered;

FIG. 2 is a similar view of the system at a subsequent stage of itsoperation, and particularly wherein the control piston has reached theupper limit of its reciprocation and the slave piston its lower limit,and during shifting of the reversing valve to a position for reversingthe direction of reciprocation of the two pistons;

FIG. 3 is another view similar to FIGS. 1 and 2, but wherein thereversing valve has shifted to cause the control piston to start itsdownward movement and the slave piston to start its upward movement;

FIG. 4 is a further view similar to FIGS. 1 to 3, but wherein thecontrol piston has reached its lower limit of reciprocation and theslave piston its upper limit, and further wherein the reversing valvehas started to shift back to the position of FIG. 1 in order to againreverse the reciprocation of the pistons;

FIG. 5 is still another view similar to FIGS. 1 to 4, but showing thesystem during the initial stage of the starting of same;

FIG. 6 is a still further view similar to FIG. 5, but showing the systemduring a subsequent stage of the starting of same, and particularlywherein excess hydraulic fluid is being dumped from the slave cylinderso as to bring the two pistons into proper phase; and

FIG. 7 is an enlarged detail view, partly in section, of the reversingvalve and pilot valve therefor shown in each of FIGS. l to 6.

With reference now to the details of the above-described drawings, thesystem, which is indicated in its entirety by reference character Itincludes a first cylinder 11 having a piston 12 reciprocable therein anda second cylinder 13 having a piston :14 therein. The cylinder 11 andpiston 12 are conventionally termed the control cylinder and pistonsince the movement of the latter controls shifting of the reversingvalve, while the cylinder 13 and piston 14 are normally called the slavecylinder and piston since they act responsive to the others.

A rod 15 is connected to control piston 12 and a rod 16 to slave piston14, each rod extending through the lower endof its respective cylinderfor connection to a load bearing element. As previously indicated, eachof such elements may comprise a piston disposed within the cylinder of adown-the-hole pump for raising well fluid therefrom. On the other hand,one of the rods 15 and 16 may be connected to a counterbalancing elementsuch as a piston disposed within an air cylinder or the like for loadingsame. In either case, and as will be described hereinafter, the pistons12' and 14 reciprocate in opposite directions so that the load-bearingelement suspended from one is moving downwardly while the other ismoving upwardly.

There is a pump 1'] connecting on its suction side with anon-pressurized or atmospheric reservoir 17a of hydraulic fluid and onits discharge side with an inlet 18 to a reversing valve 19. There is apiston 22 shiftable between positions within the reversing valve fordelivering pumped power fluid from the inlet to one of the conduits 20or 21 connecting such valve with the upper sides of control piston 12and slave piston 14, respectively. Power fluid from the upper side ofthe other cylinder piston is at the same time exhausted through outlet23 from the valve back to the reservoir 17a. Thus, for example,

with the reversing valve piston 22 disposed in the position of FIG. 1,the pumped fluid is directed through conduit 21 to the upper side ofslave piston 14 to urge the same downwardly, while hydraulic fluid onthe upper side of control piston 12 is returned through conduit 20 tothe hydraulic fluid reservoir 17a as such control piston moves upwardly.

More particularly, the lower sides of the slave pistons 12 and 14 arefluidly connected to one another by a balance line 23a connecting withthe lower ends of cylinders 11 and 13. In this manner, and as will beunderstood from the description to follow, the rod weight upon thepiston being raised (control piston 12 in FIG. 1) is counterbalanced bythe weight of the rod upon the other piston (slave piston 14 in FIG. 1).Although a perfect balance assumes equal rod weights, among otherthings, the counterbalancing eflect will be at least partial under anycircumstances, thereby resulting in a net power 1 consumption about thesame as would occur in the case of equal loadings. That is, even thoughthe power pump 17 will work harder in one-half of the cycle, it willhave a correspondingly lighter load during the other half. Theshortcoming of this latter arrangement is, of course, that the ratedcapacity of the power pump will have to be large enough to handle thehigh side of the cycle.

I have used the terms upper and lower in designating the opposite sidesof the pistons 12 and 14 as this is their normal orientation when thesystem is used in raising and lowering load bearing elements. Thus, theupper side of each such piston is the side opposite that from which therod extends, while the lower side thereof is the side from which suchrod extends.

In analyzing the forces in the system, it Will be appreciated that thefluid in the balance line 23a and beneath the pistons 12 and 14 will beat a pressure due to the combined weight of the well fluid or otherloading element and the rod on the piston which is being raised.Inasmuch as the rod weight of the piston being raised iscounterbalanced, the pressure of the power fluid from pump 17 will beonly that necessary to lower the other piston in order to raise the wellfluid. The system will also contain fluid communicating with thereservoir 17a and thus at substantially atmospheric pressure, or lessthan either the pump pressure or the balance line pressure. In theoperation of the system, the fluid beneath pistons 12 and 14 istherefore always at a higher pressure than that above the pistons, thedifference depending on Whether the upper side of the particular pistonis being subjected to power fluid or is in communication withatmospheric pressure.

Thus, with reference to FIG. 1, power fluid from the pump 17 acting uponthe upper end of slave piston 14 is opposed by fluid at substantiallyatmospheric pressure acting upon the upper side of control piston 12, sothat the slave piston moves downwardly as the control piston movesupwardly, the output of the pump 17 being only that necessary toovercome the weight of the fluid being raised by the rod 15. When,however, the pistons 12 and 14 reach their limits of reciprocation, asshown in FIG. 2, the reversing valve piston shifts, as shown in FIG. 3,so that power fluid from pump 17 is directed to the upper side of thecontrol piston 12 and the upper side of slave piston 14 discharges tothe reservoir 17a, whereby the pistons are caused to reverse theirreciprocation. When the pistons reach their opposite limits ofreciprocation, as shown in FIG. 4, the valve piston 22 is again shiftedback to the position of FIG. 11 so as to again direct hydraulic fluidfrom the pump 17 to the upper end of the slave piston, while dischargingfluid from the upper end of the control piston back to the reservoir17a, this shifting resulting in a further reversal of reciprocation ofthe cylinder pistons.

In accordance with this invention, I accomplish this automatic shiftingof the reversing valve piston 22 by means of conventionalvalve-controlled shifting lines 24 and 25 connecting with the controlcylinder 11 at spacedapart levels therein with a pilot valve 26 for thereversing valve. I have found this to be possible by taking advantage ofthe fact that the pressure of the balance line fluid is ordinarilysufliciently greater than that of the pumped power fluid to permit it tobe used as a control fluid in actuating both the pilot and reversingvalves. More particularly, I have found this necessary pressurediflerential to occur in systems of this type when employed in thepumping of wells or in other applications where the rod weight is animportant factor.

Thus, I apply the balance line fluid to one end of the reversing valvepiston and to one end of a piston 29 reciprocable in the pilot valve toshift each of them to one position, and then use the valve-controlledlines 24 and 25 to alternately admit such fluid to and exhaust it fromthe other ends of the pistons in order to shift them to and from thefirst-mentioned position. With reference 'now to the details of thismeans for reversing the piston 22, there is a line 27 common to theshifting lines 24 and 25 which connects with the body 28 of pilot valve26 on one side of the piston 29 reciprocable therein. The opposite endof pilot valve piston 29 is connected with an end of reversing valvepiston 22 by means of a conduit 30 extending between the pilot valvebody 28 and the body 31 of reversing valve 19. A further conduit 32connects the body of pilot valve 26 with the reversing valve body 31 onthe opposite side of reversing valve piston 22.

As is apparent from the drawings, the left-hand ends 22b and 29b of thepistons 22 and 29, respectively, are

These smaller ends of the pistons are fluidly connected with balanceline pressure through a conduit 33 connecting the balance line 24 withthe left-hand end of reversing valve body 31. Since the smaller ends ofpistons 22 and 29 are thus at all times subjected to balance linepressure, the pistons 22 and 29 will be maintained in their rightmostpositions, as shown in FIG. 1, as long as their opposite larger ends aresubjected to a considerably lesser pressure, as is the case of the powerfluid as well as the pressure within the reservoir 17a.

However, when the control piston 12 moves upwardly to the position ofFIG. 2, fluid beneath such piston passes through conduits 24 and 27 tothe larger end 29a of pilot valve piston 29 so as to shift it to theleft. This shifting connects balance line fluid with the conduit 32 andthus with the larger end 22a of the reversing valve piston, which inturn causes the latter to shift to the left and thereby direct powerfluid from the pump 17 to the upper end of the control piston 12 Whilepermitting fluid i on the upper end of the slave piston 14 to return tothe 1 reservoir 17a, as shown in FIG. 3. i

This passage of balance line fluid into the pilot valve 26 is controlledby means of an upwardly seating check valve 24a in shifting line 24 aswell as an upwardly seating check valve 25a in shifting line 25. Thatis, the movement of control piston 12 above the shifting line 24 willopen valve 24a While the valve 25a remains seated. When, however, thecontrol piston 12 moves downwardly past the connection of shifting line24 with the control cylinder, as shown in FIG. 3, the balance line fluidwill move the check valve 24a upwardly into isieafied position againstthe lesser pressure of the power Valve 24a will remain seated so as tomaintain the balance line fluid upon the right-hand end 29a of pilotvalve piston 29 until such time that the control piston 12 moves belowthe connection of shifting line 25 with the control cylinder, as shownin FIG. 4. At this time, the balance line fluid will unseat the valvemember 25a and thus be vented into the control cylinder 11 forexhaustion to the reservoir. When the pressure of the fluid within thepilot valve body 28 on the right-hand end of the piston 29 drops belowbalance line pressure, the

balance line pressure on the left end of the piston will quicklycause itto shift to the right. This, in turn, will also cause the reversingvalvepiston 22 to move to the right by'Vir-tue of the fact that balance linefluid on the right-hand end 22a of piston 22 is connected throughconduits32 with the reservoir 17a.

For this latter purpose, there is another conduit 34 which connectsintermediate portions of the pilot and reversing valve bodies forcommunication at all times with the outlet or return line 23 to-thehydraulic fluid reservoir 17a. In the right-hand position of the pilotvalve piston 29, the conduit 34 is connected to the conduit 32 so thatthe pressure of the fluid on the righthand end of reversing valve piston22 may be vented to atmosphere, as above described. On the other hand,andasdescribed above, the shifting of the pilot valve piston to-theleft, as shown in FIG. 2, will connect the conduit 32 with balance linefluid on the left end 29b of such piston.

During operation, there will be some leakage of hydraulic fluid fromdifferent parts of the system. In accordance with another novel aspectof the present invention, this fluid is replenished or replaced by meansof a separate pump 35 having its suction side connected to the reservoir17a, similarly to the pump 17, and its discharge side' connected with aconduit 36. This last conduit is, in turn, connected to the conduit 33between balance line 23a and the reversing valve body 31 adjacent thesmaller end 22b of piston 22. This pump 35 operates continuously so asto replenish fluid as needed, and in response to out of phase movementof the pistons 12 and 14. Its provision separate from and in addition topump 17 is a considerable improvement over most prior systems wherein asingle power unit provides the power. fluid as well as replenishing lostfluid, because it avoids the necessity of employing the high capacity,relatively low' pressure pump 17 at the higher pressure required' inpumping against balance line pressure. That is, the pump 35 may be a lowcapacity, high pressure pump suitable for this purpose.

Inevitably, the fluid replenished by' pump 35 will be in excess of thatlost, so that some means must be provided for dumping the excess fluidin order to keep the reciprocation of pistons 12 and 14 in phase. Thisis accomplished, in accordance with another novel aspect of myinvention, by means of a line 39' connecting slave cylinder 13 at alevel just above the upper limit of reciprocation of slave piston 14'with conduit 21. Thus, when excess hydraulic fluid. is put into thesystem, the slave piston 14 will move above its upper limit ofreciprocation, as shown in FIG. 6, to exhaust balance line fluid onitslower side through conduit 39 into conduit 21 andTthus t-hrough return23 to the reservoir 17a.. As will be appreciated, this-requires only thedump line 39, apart from any'valving in addition to that necessarilyprovided in the reversingv valve 19 for alternately delivering powerfluidto the upper sides of pistons 12 and 14. Infact, if desired, the.dump line may be connected directly to the reservoir, although thearrangement shown reduces piping to a minimum.

There is a. choke 40 disposed in the conduit 32. Adjustment of thischoke permits the operator toregulate the speed with which the reversingvalve piston 22 is shifted, thereby avoiding shocks in the system at thelimits of reciprocation of the control and slave pistons.

Operation When the system is first started, both pistons 12 and 14 willordinarily be resting on thebottom of their respective cylinders. Bothpumps 17 and 35 are then started, particularly in the event they aredriven by the same" prime mover. The pump 35- will immediately build uppressure in the balance line 23a so as to shift both the pilot valve andreversing valve pistons to the right, or the position shown in FIG. 1.This pressure from the pump 35 will also move the control piston 12upwardly, while the slave 6 piston 1'4 is held down on the bottom of itscylinder 13 by virtue of the fact that power. fluid is acting upon itsupper side and the upper end of the control piston is exhausting toatmosphere. As the control piston moves upwardly, fluid from pump 17 isby-passed into the reservoir 17a through relief valve 37.

When the control piston 12 is raised above the connection of shifting.line 24 with its cylinder, the pilot valve piston as well as thereversing valve piston will be shifted to-the left, for reasonspreviously described. This shift ing of the reversing valve, and thusthe direction of power fluid to the upper side of the control piston 12and exhaustion of such fluid from the upper side of the slave piston,will move the former downwardly and raise the slave piston from thebottom of slave cylinder 13. Obviously, since the slave piston wasoriginally positioned beneath its normal lower limit of reciprocation,additional fluid must be pumped into the system through the pump 35before the slave piston will be raised to its upper limit ofreciprocation. I have found, however, that this additional fluid will beput into the system upon a relatively small number of reciprocations ofthe two pistons. In other words, the slave piston will quickly rise to aposition in which'it rises slightly above the intersection of dump line39 with slave cylinder 13, so that the control and slave pistons arebrought into phase with one another.

As an alternative to the starting procedure above described, theoperator may first close the cushioning choke 40 while the two pistons12 and 14 are disposed in the lower ends of their cylinders. As in theother procedure, this will shift the pistons in both valves to the rightand also raise control piston 12. However, since the choke 40 is closed,the reversing valve piston 22 cannot shift to the left upon shifting ofthe pilot valve piston 29', and the control piston will continueupwardly into engagement with the top of cylinder 11.

As the control piston 12 is held against the upper end of its cylinder,hydraulic fluid pumped by the pump 35 will by-pass through relief valve38 in the conduit 36 into reservoir 17a. The choke 40 is then opened sothat the reversing valve piston is also shifted to the left to permitthe normal downstroke of the control piston 12 and upstroke of slavepiston 14. Since excess fluid was introduced into the system by the pump35 in moving the control piston to the top of its cylinder, the slavepiston will move above dump line 39 before control piston 12 reaches itslower limit and stay in such position and dump excess fluid from itslower side until the control piston reaches its lower limit to causefurther shifting of the pilot and reversing valves.

In order to deactivate the system for any reason, the operator need onlyshut down the pumps 17 and 35 ahd then open the relief valve 38. Thiswill drain hydraulic fluid from beneath the control and slavesystems topermit them to rest on the bottom of their cylinders and relieve allpressure from the system.

With reference now to the details of the valves shown in FIG. 7, thebody 31 of the reversing valve 19 has a smooth bore 41 in which thepiston 22 is sealably slidable between the alternate positions of FIG. 1and FIG. 3. As shown in FIG. 7, this piston is disposed in its rightmostposition wherein it connects the inlet 18 which leads from the outlet ofthe pump 17 with an opening 42 in thevalve body connectable to conduit21 leading to the upper end of slave cylinder 14, while at the same timeconnecting the return line 23 with a secondopening 43. thereinconnectable with conduit 2G leading to the upper end of the controlpiston 12. As also shown in FIG. 7, the piston 29 of pilot valve 19 isalso in its rightmost position. to connect theconduit 32' with conduit34 connecting through the reversing valve with the return line 23 soasto subject the right-hand end 22a of reversing valve piston 22 to theexhaustpressure.

At the same time, balance line pressure is admitted through conduit 33connecting with port 43 in the lefthand end of reversing valve body 31so as to subject the smaller, left-hand end 22b of the reversing valvepiston to balance line pressure. This same pressure is also admitted tothe smaller, left-hand end 29]; of the pilot valve piston 29 throughpassageways 44 and 45 in the reversing valve and pilot valve bodies,respectively, connecting with the passageway 30 therebetween. Theconduit 27 from the shifting lines 24 and 25 of the control cylinderconnects with the inlet 46 in the right-hand end of the pilot valve bodyfor admitting the exhaust or atmospheric pres sure to the larger,right-hand end 29a of pilot valve piston 29.

The reversing valve piston 22 has annular recesses formed along itslength intermediate a left-hand enlargement 47, intermediateenlargements 48 and 49, and righthand enlargement 50 thereon. Theleft-hand enlargement 47 is sealably slidable within a reduced section51 of the reversing valve body bore so as to define the smaller pressureresponsive area on the end 22b of the piston. On the other hand, theright-hand enlargement 50 on the piston 22 is sealably slidable withinan enlarged portion 52 of such bore so as to define the larger pressureresponsive area on the end 22a of the piston. Each of the intermediate'enlargements 48 and 49 is also sealably slidable within the enlargedsection 52 of the bore, and the leftmost 48 of these intermediateenlargements is engageable with a reduced shoulder 53 in the bore tolocate the piston 22 in the left-hand position of FIG. 3.

There is a passageway formed centrally of the piston 22 comprising anopening 54 extending axially thereof and connecting with lateral ports55 and 55a therein. As can be seen from FIG. 7, when the piston 22 isshifted to the right-most position, the annular enlargements 48 and 4-9are disposed on opposite sides of the connection of inlet 18 and opening42. On the other hand, the recessed portion of the piston 22intermediate these enlargements is imperforate to form an annularpassageway between the valve body and the piston which, as

previously described, directs pumped fluid from the inlet 18 through thereversing valve into the opening 42 connecting with conduit 21, which inturn leads to the upper end of slave piston 14. At the same time, thepiston enlargements 47 and 4 8 are disposed on opposite sides of theconnection of return line 23 and opening 43 with the valve body.Furthermore, the recessed portion of the piston 22 intermediate theseenlargements is also imper-forate to define another annular passagewaythrough which the upper end of control piston 12 is exhausted to thereservoir 17a into which the return 23 discharges. It will also be notedthat the conduit 34 connects with ports 56 and 57 in the pilot andreversing valve bodies, respectively, to connect the conduit 32 withthis same annular passageway within the reversing valve so that, againas previously mentioned, the fluid on the right-hand end 22a of thepiston 22 is also exhausted to atmosphere.

When the piston 22 shifts to the left-hand position shown in FIG. 3, theenlargements 49 and 50 on the spool type piston are disposed on oppositesides of the opening 42 from the valve body so as to connect suchopening with the port 55a in the piston and the longitudinal opening 54through the piston and its other lateral port 55. The intermediateenlargement 48 on the piston has moved to a position intermediateopening 43 and return line 23. Since the port 55 is to the left of thisenlargement 48, the opening 42 is thereby connected with the return line23 so that fluid on the upper end of slave piston 14 and conductedthrough conduit 21 is exhausted to the atmosphere. At the same time, theinlet 18 is connected with opening 43 by virtue of the disposal ofenlargement 48 to the left of opening 43 and the disposal of enlargementbore 58 in which the piston 29 is slidable. This piston outwardly urgedrings 64a.- This has been made possible by the machining of annularpressure equalizing has a reduced section 59 slidable within a reducedend 58 of the bore to define the smaller pressure responsive area of theleft end 29b of the piston. An enlarged section 60 of the piston issealably slidable within an en-. larged portion 61 in the pilot valvebody to define the larger pressure responsive area on the end 29a of thepiston 29. The left end of the enlarged section 60 is engageable with ashoulder 62 intermediate the two sections of the bore to locate thepiston 29 in its left-hand position of FIG. 3.

There is a passageway 63 extending longitudinally and laterally throughthe piston 29 to connect its left-hand end 29b with an intermediateportion of its enlargement 60'. With the piston 29 in the right-handposition of FIG. 7, the enlargements 59 and 60 are disposed on oppositesides of the connection of conduit 32 with the valve body as well asport 56 connecting the conduit 34 therewith. Thus, as previouslydescribed, the conduit 32 is connected to port 56 through the annularpassageway between the valve body and piston to exhaust the larger endof piston 22 to the return line 23 to the reservoir. At the same time,the lateral connection of passageway 63 is disposed between spaced-apartsealing portions on the enlargement 60 so as to seal off such passagewayand thereby prevent the escape of balance line fluid from the left-handend 2% of the pilot valve piston. As previously described and as shownin FIG. 1, the right-hand end 29a of such piston is, at this time,exhausting through inlet 27 so that the piston 29 is maintained in itsright-hand position.

However, upon movement of the control piston 12 to its upper limitedposition, whereby balance line fluid is admitted through inlet 27 to theright-hand end 29a of the pilot valve piston, the latter is caused tomove to the left. In the leftmost position of the piston 29, theenlargements 59 and 60 are disposed on opposite sides of the port 56 soas to isolate conduit 34 from conduit 32. At the same time, thespaced-apart sealing portions of the enlargement 60 are disposed onopposite sides of the connection of conduit 32 with the pilot valve bodyso as to connect the passageway 63 with such conduit. This, of course,permits the balance line fluid on the left-hand end 2912 of the piston29 to flow through conduit 32 and against the right-hand end 22a of thereversing valve piston 22, thereby shifting it to the left in the mannerpreviously described.

The sealing portions on the enlargements 59 and 60 of piston 29 areprovided by outwardly urged rings 64 of conventional construction. Inthe case of the enlargement 60, the rings 64 are arranged inspaced-apart pairs to define an annular recess 65 connecting with thelateral porize the pressure about the piston and thus prevent it frombinding in the bore of the valve body. In order to provide asatisfactory seal between such a piston and the bore of the valve body,it has also been conventional to grind or hone the latter. Thisexpensive procedure has been followed, despite the fact that the use ofoutwardly urged sealing rings would be cheaper and would operateWithless leakage and in more extreme temperature conditions, becausesuch rings would expand and hang up in the undercut annular grooves.

However, in accordance with another novel aspect of my invention, thevalve 19 is of such construction that the sealing portions on theenlargements 47 to 50 of the piston 22 may also comprise theconventional type of recesses on the outside, rather than the inside, ofthe valve body, as shown in FIG. 7 at 66 and 67 opposite openings 42 and43 in the valve body. Moreparticularreference to other features andsubcombin-ations.

ly, these openings to the bore of the valve body are connected with theannular recesses 66 and 67 by means of ports 68 and 69 formed throughwebs 70 and 71, respectively, having inner surfaces which form a smoothcontinuation of the bore of the valve body. Obviously, therefore, thesealing rings 64:: will slide freely over the ports 68 and 69 duringshifting of the piston 22. Preferably, the webs 70 and 71 are formed bymachining the recesses 66 and 67 to a depthcorresponding to the outersurfaces of the webs. As shown, certain of the circular ports 68 and 69may be provided with longitudinal extensions on each side.

The outer sides of the annular recesses are closed by means of annularsleeves 73 and 74 welded or otherwise secured to the exterior of thevalve body. Thus, as can be :seen trom FIG. 7, the provision of aseparate body for the reversing valve, as well as the cylindricalconstruction of the right-hand end of the reversing valve body, enablethe sleeves 73 and 74 to be merely moved over and then secured in placeabout the recesses.

From the foregoing it will beseen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the appara-tus.

It will be understood that certain features and subcombinations are ofutility and may be employed without This is contemplated by and iswithin the scope of the claims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. An hydraulicpumping system, comprising a pair of cylinders each having a pistonreciprocable therein, a rod extending from each piston through thecylinder for connection to a load to he raised, a balance line fluidlyconnecting the cylinders to one another below the pistons, meansshiftable between positions for alternately delivering hydraulic fluidto the upper end of one piston while exhausting it from the upper end ofthe other piston so as v to reciprocate the pistons in oppositedirections, a first line connecting with the one cylinder below theupper limit of reciprocation of the piston therein and having a checkvalve movable to an open position when said piston reaches said upperlimit to admit balance line fluid to said shiftable means, and a secondline connecting with the one cyinder above the lower limit ofreciprocation of the piston therein and having a check valve movable toan open position when said piston reaches said lower limit to exhaustbalance line fluid from said shiftable means.

2. An hydraulic pumping system, comprising a pair of cylinders eachhaving a piston reciprocable therein, a rod extending from each pistonfor connection to a load to be raised, a reversing valve having a pistonreciprocable therein between alternate positions for admitting hydraulicfluid to the upper end of one cylinder piston while exhausting it fromthe upper end of the other cylinder piston, whereby the cylinder pistonsreciprocate in opposite directions, a balance line fluidly connectingthe lower ends of the cylinder pistons to one another and the one end ofthe valve piston which is smaller than the other, and means for shiftingthe valve piston between said alternate positions includingvalve-controlled lines for connecting the larger end of the valve pistonwith the fluid communicating with alternate sides of the piston in onecylinder as said cylinder piston reciprocates therein.

3. An hydraulic pumping system of the character defined in claim 2.,wherein said lines are connected to the one cylinder at spaced-apartlevels for admitting balance line fluid to the larger end of said valvepiston, when said one cylinder piston reaches its upper limit ofreciproca- 10 tion, and exhausting said fluid therefrom when said onecylinder piston reaches its lower limit of reciprocation;

4. An hydraulic pumping system, comprising a pair of cylinders eachhaving a piston reciprocable therein, a rod extending from each pistonand through the cylin der for connection to a load-bearing element, areversing valve including a piston shiftable between a first positionfor admitting hydraulic fluid to one cylinder on the upper side of thepiston therein while exhausting hydraulic fluid from the other cylinderon the upper side of the piston therein, and a second position foradmitting hydraulic fluid to the other cylinder on said upper side-ofitspiston while exhausting hydraulic fluid firom the one cylinder on said.upper side of its piston, a balance line fluidly connecting thecylinders on the lower sides of their pistons, and means includingvalve-controlled lines connecting with said one cylinder for shiftingsaid reversing valve piston from said first to said second position,when the piston in said one cylinder reaches a limited position in onedirection of its reciprocation, and then shifting said reversing valvepiston from said second to said first position, when said cylinderpiston. reaches a limited position in the other direction of itsreciprocation.

5. An hydraulic pumping system of. the character defined in claim 4,wherein said last-mentioned means includes a fluid connection betweenthe balance line and one end of the reversing valve piston, and a pilotvalve for admitting balance line fluid to the other end of. saidreversing valve piston when said cylinder piston reaches its limitedposition in one direction and exhausting said fluid from said other endof the. reversing valve piston when the cylinder piston reaches itslimited position in the other direction.

6. An hydraulic pumping system, comprisinga pair of cylinders eachhaving a piston reciprocable therein between limited positions, a rodextending from each piston and through the cylinder for connection to aload-bearing element, a reversing valve, a pump, means for deliveringhydraulic fluid from the pump to the reversing valve and for returningit from said reversing valve to said pump, conduits connecting thereversing valve with said cylinders on the upper sides of the pistonstherein, a piston reciprocable within the reversing valve betweenpositions for alternately connecting the pump inlet to one conduit whileconnecting the other conduit with the pump return, a balance linefluidly connecting the cylinders on the lower sides of the pistons toone another and the reversing valve on an end of the piston thereinwhich is smaller than the other end, and means includingvalve-controlled lines connecting with one cylinder for admittingbalance line fluid to the other end of the reversing valve piston, whenthe piston in said cylinder reaches one limited position, and exhaustinghydraulic fluid from said other end of the reversing valve piston, whensaid cylinder piston reaches its other limited position.

7. An hydraulic pumping system of the character defined in claim 6,wherein one line has a check valve therein adapted to open when saidcylinder piston reaches one limited position, and another line has acheck valve therein adapted to open when said cylinder reaches saidother limited position.

8. An hydraulic pumping system of the character defined in claim 6,wherein said last-mentioned means includes a pilot valve having a pistonreciprocable therein, said pilot valve piston having a larger endconnected with said valve-controlled lines and a smaller end fluidlyconnected to the balance line, and means responsive to reciprocation ofthe pilot valve piston for alternately admitting balance line fluid tothe larger end of the reversing valve piston and exhausting balance linefluid from said larger end of the reversing valve piston.

9. An hydraulic pumping system of the character defined in claim -6,including means for controlling the rate of admission and exhaustion offluid to and from the larger end of the reversing valve piston.

1 1 I 10. -An hydraulic pumping system of the character defined in claim6, including means for replenishing balance line fluid and for dumpingexcess balance line fluid from between the sides of the cylinder pistonsfrom whiclrthe rods extend.

11. An hydraulic pumping system of the character defined in claim 10,wherein said replenishing means includes another pump, and including acommon source of hydraulic fluid for both pumps.

12. An hydraulic pumping system of the character defined in claim 10,wherein said dumping means includes a line connecting with the othercylinder at a level above the one limit of reciprocation of the pistontherein for returning said fluid to said pump.

13. An hydraulic pumping system, comprising a pair of cylinders eachhaving a piston reciprocable therein between limited positions, a rodextending from each piston through the cylinder for raising a loadconnected thereto, a balance line fluidly connecting the cylinders toone another on the lower sides of the pistons, means for deliveringhydraulic fluid to the balance line and alternately to the upper end ofone piston while exhausting it vfrom the upper end of the other pistonso as to reciprocate them in opposite directions, and a line connectingwith one of said cylinders above the upper limit of reciprocation of thepiston therein for dumping fluid from a of said bores between first andsecond positions, one end inlet to the pilot valve bore on the largerend of its piston, a port connecting with the reversing valve bore onthe smaller end of the piston therein, an inlet to and outlet from thereversing valve bore, first and second openings in the reversing valvebore, passageways in the reversing valve connecting the inlet to thereversing valve bore with the first opening and the outlet therefrom tothe second opening, in the first position of said piston, and connectingsaid inlet with the second opening and said outlet with the firstopening in its second position, a first conduit connecting the pilotvalve bore with the larger end of the reversing valve bore, andpassageways in the pilot valve connecting the first conduit-with thesecond conduit in a first position of the pilot valve piston andconnecting its smaller end with the first conduit in a second positionthereof. Q

16. Valve apparatus of the character defined in claim 15, wherein saidreversing valve piston has outwardly urged sealing rings thereabout andannular recesses intermediate the rings to form part of the passagewaystherein, and said reversing valve bore has an annular recess at each ofsaid openings therein and connecting with said bore through ported websforming a smooth continuation of the bore.

17. Valve apparatus of the character defined in claim 16, wherein saidbody means comprises separate reversing valve and pilot valve bodies,and there are sleeves 'slidably received over an end of the reversingvalve body and secured over the annular recesses thereabout.

References Cited in the file of this patent UNITED STATES PATENTS2,024,252 Romaine et a1. Dec. 17, 1935 2,355,669 Moser Aug. 15, 19442,575,241 White Nov. 13, 1951 Witt Janv 4, 1955

1. AN HYDRAULIC PUMPING SYSTEM, COMPRISING A PAIR OF CYLINDERS EACHHAVING A PISTON RECIPROCABLE THEREIN, A ROD EXTENDING FROM EACH PISTONTHROUGH THE CYLINDER FOR CONNECTION TO A LOAD TO BE RAISED, A BALANCELINE FLUIDLY CONNECTING THE CYLINDERS TO ONE ANOTHER BELOW THE PISTONS,MEANS SHIFTABLE BETWEEN POSITIONS FOR ALTERNATELY DELIVERING HYDRAULICFLUID TO THE UPPER END OF ONE PISTON WHILE EXHAUSTING IT FROM THE UPPEREND OF THE OTHER PISTON SO AS TO RECIPROCATE THE PISTONS IN OPPOSITEDIRECTIONS, A FIRST LINE CONNECTING WITH THE ONE CYLINDER BELOW THEUPPER